This invention relates generally to the control of automated processes, and, more particularly, to an automation control apparatus for determining the presence of articles meeting acceptability criteria.
In modern production line operations, machines are often highly dependent upon each other, and errors by one machine may not be readily detected by other machines. Consequently, errors by one machine, or problems arising after an article leaves one machine but before it arrives at the next machine, may not be immediately discovered, so that the problem is propagated through the remainder of the automated operation.
As an example, problems can often arise at the end of the production line at the packaging station. If a fixed number of a single article is to be inserted into one package and a feed machine supplies a different number to the packaging machine, the wrong number of articles may be packaged. Or, if fixed numbers of several different articles are to be packaged together, a malfunction by any one of the machines feeding the articles to the packaging machine can result in an package containing incorrect contents. Similar problems can arise in other automated contexts, as, for example, an assembly machine that receives the wrong parts to be assembled.
There are several well established approaches for avoiding these kinds of problems in automated operations. Human operators and inspectors are sometimes provided at various points to oversee the operations, or inspect or count articles. The use of this human intervention is undesirable, in that the work is often unfulfilling and dull for the worker, and has the result that errors often arise in spite of the human presence. Human labor is also expensive, detracting from the full automation of the operation. Human intervention is sometimes not practical, as where monitoring involves very rapid response or making fine distinctions that are beyond human capability. A human being cannot properly count and verify the identity of, for example, 50 articles per second passing to a packaging machine.
Automatic process controls suitable for use in a production line environment are also known. The most common such controls are scales for weighing articles and photosensor systems wherein the presence of an article may be detected by the breaking of a light beam. Although relatively simple in operation, each of these approaches has distinct drawbacks. Neither weighing nor a light beam can detect when the wrong piece is present, if the piece has generally the same weight and shape as the intended article. Thus, for example, a bolt could be mistakenly packaged instead of a washer having the same weight, or a number of lighter articles could be mistaken for a heavier article, in an apparatus using scales to monitor packaging. Moreover, if the scale apparatus itself malfunctions as by hangup of an article when the articles are removed from the scale, the same article may be weighed repeatedly but never be packaged.
Use of light beams suffers from the problem that they cannot be used in many dirty environments due to interference with the beam, and also cannot be used in conjunction with certain oddly shaped articles or transparent articles. Weight and light beam systems also cannot provide information about, or control over, articles that may be present but misoriented, where the misorientation is critical.
The existing process control systems are also not well adapted to the control of time-sequenced operations requiring, for example, that different parts arrive at a station in some predetermined sequence. It is not now generally possible to determine whether the necessary numbers of the proper articles arrive at the right time, except in a few situations.
Accordingly, there has been a need for an apparatus which allows the determination of the presence of an object, and further allows the analysis of the object to be certain that it is the right article, all of this being operable in adverse environments. The apparatus should also allow control of time-sequenced operations involving various types of parts. The present invention fulfills this need, and further provides related advantages.